docs: def add_alias(self, alias, indices, **kwargs):
          """
          Add an alias to point to a set of indices.
          (See :ref:`es-guide-reference-api-admin-indices-aliases`)
  
          :param alias: the name of an alias
          :param indices: a list of indices
  
          """
          indices = self.conn._validate_indices(indices)
  
          return self.change_aliases(['add', index, alias,
                                      self._get_alias_params(**kwargs)]
                                      for index in indices)